The AM Forum

Need suggestions as to methods for getting rid of RFI in an EQ/Limiter/Compressor.  Input and output cables are shielded and unit works fine when transmitting into a dummy load but not when its to the antenna.  RF seems to be getting in via the output cable.  Anyone else had this probloem?   ??? ???

Clamp on ferrite things they use on much electronics are easy.
I got thousands free at work.
Dont forget the AC line cord.

I never seem to have RF in the shack, even though the antenna is over the house.
Good grounds, a resonant antenna, no tuner, everything mounted in cabinets (which are grounded).

I did use a bunch of those things on my flex ins and outs though...

It seems to me that the rf field strength would have to be very high, or the grounding very poor to get RF into things.

I 'can' run 700 watts carrier and well over 2kw pep with the antenna drirectly above the shack up about 50 feet without issues.

Brett
 


 

Move the antenna farther away Roy.   :D

Are you using unbalanced audio cables? My RFI went away when I changed to balanced cables.

Yep. This curred my problems.   I used balanced XLR to XLR cables. Then an audio technica Low to high impedance converter at the transmitters.  This solved all my issues. 

C

Place an isolation transformer on the output.  A small 600:600 ohm audio transformer will isolate the audio ground.

I run all the audio outputs (PC & various receivers) through an 8 channel line level mixer then into a set of amplified speakers.  Each of the inputs and the output run through an isolation transformer.  No problems with RF. 

The balanced cable did the trick...Thanks guys! ;D ;D ;D

These things almost never or never have anything to do with RF distorting baseband audio.  I have experienced cases where "ground" or grounded cabinets made matters worse.  For an excellent paper on dealing with RF in the shack where it is not wanted download this file by Jim Brown and read it. 

http://audiosystemsgroup.com/RFI-Ham.pdf

73

Rob
K5UJ

Good article...